Hydrophilic membranes and method of preparation thereof (iv)

ABSTRACT

Disclosed is a hydrophilic porous membrane comprising a block copolymer of the formula: A-B-A (I) or A-B (II), wherein block A is (i) a copolymer of glycidol and allyl glycidyl ether, the copolymer having one or more allyl groups; or (ii) a copolymer of glycidol and allyl glycidyl ether, wherein one or more of the allyl groups of the copolymer have been replaced with 1,2-dihydroxypropyl group or a group of the formula: —(CH 2 ) a —S—(CH 2 ) b —X, wherein a, b, and X are as defined herein, and block B is an aromatic hydrophobic polymeric segment, for example, polyethersulfone. Also disclosure is a method of preparing such porous membranes.

BACKGROUND OF THE INVENTION

Aromatic polymers such as polysulfone, polyethersulfone,poly(phthalazine ether sulfone ketone), poly(p-phenylene sulfide),polyether imide, polyimide, polyphenylene oxide, polyphenylene ether,and polyether ether ketone are useful for preparing porous membranes dueto their chemical stability, processability, mechanical strength,flexibility, and thermal stability. Since these polymers are generallyhydrophobic, membranes prepared from these polymers are hydrophobic, andthus lack desirable surface properties such as wettability, low proteinadsorption, thromboresistance, and controlled surface chemicalreactivity.

Attempts have been made to improve one or more of the surface propertiesof membranes made from the aromatic polymers. For example, membraneshave been treated with high energy radiation or plasma to imparthydrophilicity. In other examples, hydrophilic monomers have beengrafted to hydrophobic membrane surfaces. Attempts also have been madeto coat the hydrophobic membrane with water soluble polymers such aspolyethylene glycol or polyvinyl pyrrolidone. The above attempts forimproving properties, particularly hydrophilicity, however, have one ormore drawbacks such as lack of reproducibility, lack of stability of themodification, and/or pore clogging.

The foregoing shows that there is an unmet need for hydrophilic porousmembranes formed from aromatic hydrophobic polymers and for a method ofimparting hydrophilicity to membranes formed from aromatic hydrophobicpolymers.

BRIEF SUMMARY OF THE INVENTION

The invention provides hydrophilic porous membranes formed from aromatichydrophobic polymers and for a method of imparting hydrophilicity tomembranes formed from aromatic hydrophobic polymers.

Thus, the invention provides a porous membrane comprising a blockcopolymer of the formula: A-B-A (I) or A-B (II), wherein block A is (i)a copolymer of glycidol and allyl glycidyl ether, the copolymer havingone or more allyl groups; or (ii) a copolymer of glycidol and allylglycidyl ether, wherein one or more of the allyl groups of the copolymerhave been replaced with 1,2-dihydroxypropyl group or a group of theformula: —(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and Xis selected from an acidic group, a basic group, a cation, an anion, azwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy, aldehydo,amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of the formula—C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc), or asalt thereof; and block B is an aromatic hydrophobic polymeric segment.

The invention also provides a method of preparing a porous membranecomprising: (i) providing a polymer solution comprising a solvent, saidaromatic hydrophobic polymer, and said block copolymer; (ii) casting thepolymer solution as a thin film; (iii) subjecting the thin film to phaseinversion by immersion in a nonsolvent to obtain a porous membrane; andoptionally (iv) washing the porous membrane.

The present invention has one or more of the following advantages. Theinvention provides a facile method for tuning the degree ofhydrophilicity desired in a porous membrane. Block copolymers of variousdegrees of hydrophilicity are produced from aromatic hydrophobicpolymers. The composition of the block copolymers is readilycharacterized by well known techniques. The porous membranes preparedusing the block copolymers are low in extractables. The block copolymershave strong adhesion to aromatic hydrophobic polymers. The porousmembranes are stable to process conditions such as autoclaving,steaming, and isopropanol (IPA) extraction.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1A depicts the SEM image of the cross-section of a hydrophilicporous membrane in accordance with an embodiment of the invention. FIG.1B depicts a higher magnification SEM image of the cross-sectiondepicted in FIG. 1A.

FIG. 2A depicts the SEM image of the cross-section of anotherhydrophilic porous membrane in accordance with an embodiment of theinvention. FIG. 2B depicts a higher magnification SEM image of thecross-section depicted in FIG. 2A.

FIG. 3 illustrates the microstructure of a hydrophilic porous membranein accordance with an embodiment of the invention. 1 represents anaromatic hydrophobic polymer, 2 represents the aromatic hydrophobicpolymeric segment of the block copolymer in accordance with anembodiment of the invention, and 3 represents the hydrophilic polymericsegment of the block copolymer.

FIG. 4A depicts the SEM image of the cross-section of a membrane inaccordance with an embodiment of the invention. FIG. 4B depicts a highermagnification SEM image of the image depicted in FIG. 4A.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with an embodiment, the invention provides a hydrophilicporous membrane comprising a block copolymer of the formula: A-B-A (I)or A-B (II), wherein block A is (i) a copolymer of glycidol and allylglycidyl ether, the copolymer having one or more allyl groups; or (ii) acopolymer of glycidol and allyl glycidyl ether, wherein one or more ofthe allyl groups of the copolymer have been replaced with1,2-dihydroxypropyl group or a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X isselected from an acidic group, a basic group, a cation, an anion, azwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy, aldehydo,amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of the formula—C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc), or asalt thereof; and block B is an aromatic hydrophobic polymeric segment.

In accordance with another embodiment, the invention provides a methodof preparing a hydrophilic porous membrane comprising: (i) providing apolymer solution comprising a solvent, said aromatic hydrophobicpolymer, and said block copolymer; (ii) casting the polymer solution asa thin film; (iii) subjecting the thin film to phase inversion byimmersion in a nonsolvent to obtain a porous membrane; and optionally(iv) washing the porous membrane.

In accordance with an embodiment, block A is a copolymer of glycidol andallyl glycidyl ether, the copolymer having one or more allyl groups.

In accordance with an embodiment, block A is composed of polyglycerolsegments having one or more of the following repeat units:

and of poly allyl glycidyl ether segments having a repeat unit of theformula:

wherein R is allyl.

In accordance with another embodiment, block A is a copolymer ofglycidol and allyl glycidyl ether, as described above, wherein one ormore of the allyl groups of the copolymer have been replaced with1,2-dihydroxypropyl group or a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X isselected from an acidic group, a basic group, a cation, an anion, azwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy, aldehydo,amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of the formula—C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc), or asalt thereof.

In accordance with an embodiment, X can be any acidic group, forexample, sulfonic acid, phosphoric acid, phosphonic acid, or carboxylicacid, the basic group can be any basic group, for example, an aminogroup, an alkylamino group, or a dialkylamino group, the cation can beany cationic group, for example, a quaternary ammonium group, and thezwitterion can be, for example, a quaternary ammonium alkyl sulfonategroup of the formula —N⁺(R¹R²)(CH₂)_(c)SO₃ ⁻, wherein R¹ and R² arealkyl groups and c is 1 to 3.

One or more of the allyl groups on the block copolymers can be reactedwith a suitable agent to effect the desired changes. For example, theallyl group can be converted to 1,2-dihydroxypropyl groups by reactingwith an oxidizing agent such as osmium tetroxide, alkaline permanganate,or hydrogen peroxide.

The allyl group can be converted to a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X is anacidic group by reacting the allyl group with an acid group bearingthiol such as HS—(CH₂)_(b)—X, wherein X is COOH, PO₄H, PO₃H, or SO₃H,wherein b is 1 to 3.

The allyl group can be converted to a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X is abasic group by reacting the allyl group with a basic group bearing thiolsuch as HS—(CH₂)_(b)—X, wherein X is NH₂, NHR, or NRR, where R is aC₁-C₆ alkyl group, and b is 1 to 3.

The allyl group can be converted to a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X is acationic group by reacting the allyl group with a cationic group bearingthiol such as HS—(CH₂)_(b)—X, wherein X is NH₃ ⁺, NHRR⁺, or NRRR⁺, whereR is a C₁-C₆ alkyl group, and b is 1 to 3.

The allyl group can be converted to a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X is azwitterionic group by reacting the allyl group with a zwitterionic groupbearing thiol such as HS—(CH₂)_(b)—X, wherein X is group bearing azwitterion, for example, —N⁺(R)₂—(CH₂)_(c)—SO₃ ⁻, where R is a C₁-C₆alkyl group, and b and c are independently 1 to 3.

One or more of the allyl groups can be replaced by reacting with ahaloalkane thiol, for example, with a fluoroalkane thiol, a chloroalkanethiol, a bromoalkane thiol, or an iodoalkane thiol. The acyl group ofacyl alkane thiol can be formyl, acetyl, propionyl, or butanoyl. Thealkoxy part of alkoxy alkane thiol can be a C₁-C₆ alkoxy group. Thealkylthio part of alkylthio alkane thiol can be a C₁-C₆ alkyl group.

In an embodiment, one or more of the allyl groups can be reacted with acarboxylic alkane thiol or a salt thereof, a phosphoric alkane thiol ora salt thereof, a phosphonic alkane thiol or a salt thereof, a sulfonicalkane thiol or a salt thereof, a (dialkylamino)alkane thiol or a saltthereof, an aminoalkane thiol or a salt thereof, an alkylamino alkanethiol, a dialkylaminoalkane thiol, and a sulfonic alkylammonium alkanethiol or a salt thereof.

In accordance with an embodiment, the aromatic hydrophobic polymericsegment of the block copolymer is selected from polysulfone,polyethersulfone, polyphenylene ether, polyphenylene oxide,polycarbonate, poly(phthalazinone ether sulfone ketone), polyetherketone, polyether ether ketone, polyether ketone ketone, polyimide,polyetherimide, and polyamide-imide, preferably polyethersulfone.

Embodiments of the hydrophobic polymer segments include polysulfone(PS), polyethersulfone (PES), polycarbonate (PC), polyether ether ketone(PEEK), poly(phthalazinone ether sulfone ketone) (PPESK), polyphenylenesulfide (PPS), polyphenylene ether (PPE), polyphenylene oxide (PPO), andpolyether-imide (PEI), which have the following structures:

The number of repeat units, n, within each of the above aromatichydrophobic segments can be from about 10 to about 1000, preferably fromabout 30 to about 300, and more preferably from about 50 to about 250.

In accordance with an embodiment, block A is a branched copolymer.

In accordance with an embodiment, the hydrophilic porous membraneincludes a copolymer of formula (I), which has the following structure:

wherein n is 10 to 1000, preferably about 50 to 175, and more preferablyabout 60 to about 100. “Pg/PolyAGE” designates a copolymer of glycidoland allyl glycidyl ether.

In accordance with an embodiment, when polysulfone is the aromatichydrophobic segment, n is about 10 to about 1000, preferably about 30 toabout 225, and more preferably about 45 to about 130.

In accordance with an embodiment, block A is present in the copolymer inan amount of about 20% to about 50 mol % and block B is present in anamount of about 50% to about 80 mol %. Preferably, block A is present inan amount of about 40% to about 55 mol % and block B is present in anamount of about 40% to about 60 mol %.

In accordance with an embodiment, the hydrophilic porous membraneincludes a block copolymer having the following structure:

wherein R is allyl or —(CH₂)_(b)—X, wherein X is selected from amino,dimethylamino, —CH₂CH₂SO₃H, —CH₂CH₂CH₂SO₃H, —CH₂CO₂H, and—CH₂CH₂N⁺(CH₃)₃, and combinations thereof. “Pm” designates a copolymerof glycidol and allyl glycidyl ether.

In accordance with an embodiment, the hydrophilic porous membraneincludes a copolymer, wherein block A is present in an amount of about20% to about 50 mol % and block B is present in an amount of about 50%to about 80 mol %.

In accordance with an embodiment, the hydrophilic porous membraneincludes a copolymer having one of the following structures:

wherein n is about 10 to about 1000, preferably about 50 to 175, andmore preferably about 60 to about 100.

The block copolymers can be prepared by any suitable method, forexample, a method comprising:

(i) providing an aromatic hydrophobic polymeric segment having one ormore terminal functional groups selected from hydroxy, mercapto, andamino groups; and

(ii) carrying out ring opening polymerization of allyl glycidyl etherand glycidol on the aromatic hydrophobic polymeric segment.

In accordance with an embodiment, the aromatic hydrophobic polymericsegment is selected from polysulfone, polyethersulfone, polyphenyleneether, polyphenylene oxide, polycarbonate, poly(phthalazinone ethersulfone ketone), polyether ketone, polyether ether ketone, polyetherketone ketone, polyimide, polyetherimide, and polyamide-imide,preferably polyethersulfone. The aromatic hydrophobic polymeric segmentcomprises one or more, preferably one or two, terminal functional groupsselected from hydroxy, mercapto, or amino groups.

The functional groups can be provided on the aromatic hydrophobicsegments by methods known to those skilled in the art. For example,hydroxy-terminated polyether imide synthesis is described in U.S. Pat.Nos. 4,611,048 and 7,230,066. Thus, for example, hydroxy-terminatedpolyether imides can be prepared by the reaction of a bis-etheranhydride and a diamine, followed by reaction with an amino alcohol.Illustratively, a hydroxy-terminated polyether imide can be prepared bythe reaction of bis(4-(3,4-dicarboxy-phenoxy)phenyl)propane dianhydrideand m-phenylenediamine, followed by reaction with p-aminophenol.

Amine-terminated polyether imides can be prepared by the reaction of abis-ether anhydride and a diamine. Thus, for example,bis(4-(3,4-dicarboxy-phenoxy)phenyl)propane dianhydride andm-phenylenediamine can be reacted to produce an amine terminatedpolyether imide. See, for example, U.S. Pat. No. 3,847,867.

Hydroxy-terminated PEEK is described in Journal of Polymer Science PartB 2006, 44, 541 and Journal of Applied Science 2007, 106, 2936. Thus,for example, hydroxy-terminated PEEK with pendent tert-butyl groups canbe prepared by the nucleophilic substitution reaction of4,4′-difluorobenzophenone with tert-butyl hydroquinone with potassiumcarbonate as catalyst.

Hydroxy-terminated polycarbonate is described in Journal of PolymerScience: Polymer Chemistry Edition 1982, 20, 2289. Thus, for example,hydroxy-terminated polycarbonate can be prepared by the reaction ofbisphenol A and phosgene, with in situ blocking of some of the phenolicgroups either prior to or during phosgenation. Trimethylchlorosilane,trifluoroacetic anhydride, or trifluoroacetic acid can be used for theblocking. The blocking group can be removed at the end of thepolymerization.

Hydroxy-terminated PPO can be prepared as described in U.S. Pat. No.3,318,959. Thus, for example, poly-2,6-dimethylphenylene ether can bereacted with sodium hydroxide to obtain a PPO having a hydroxyl contentof 2.3 to 3 hydroxyl groups per molecule.

In an embodiment, the aromatic hydrophobic polymeric segment ispolyethersulfone having one or more hydroxy groups is of the formula:

wherein n is about 10 to about 1000, preferably about 50 to 175, andmore preferably about 60 to about 100.

Polyethersulfone is commercially available, for example, as VIRANTAGE™VW-10700 from Solvay, with the formula

which has a GPC molecular weight 21000 g/mol and OH end groups of 210μeq/g; as VIRANTAGE VW-10200 from Solvay with the formula

which has a GPC molecular weight of 44,200 g/mol and OH end groups of 80μeq/g; and as SUMIKAEXCEL™ 5003PS from Sumitomo with the formula

which has a reduced viscosity of 0.50 [1% PES dissolved in DMF] and OHend groups in the range of 0.6-1.4 per molecule.

Glycidol or 2,3-epoxy-1-propanol contains one epoxide ring and onehydroxyl group as functional end groups. Both ends are capable ofreacting with each other to form macromolecules which are glycerolderivatives. The resulting macromolecules continue to react to formpolyglycerol. Allyl glycidyl ether contains one epoxide ring, which iscapable of undergoing ring opening polymerization.

The opening of the epoxide ring of glycidol or allyl glycidyl ether isinitiated by the nucleophile, i.e., oxide anion, amino group, or sulfideanion, of the aromatic hydrophobic polymeric segment, which is presentas the terminal functional group (amino group) or is produced by thereaction of the terminal group (OH or SH) on the aromatic hydrophobicpolymeric segment with the base employed in the reaction. The ringopened epoxide continues to open the epoxide of the next glycidol and/orallyl glycidyl ether in the presence of a base, and the polymerizationof glycidol and allyl glycidyl ether proceeds in this manner. When SHacts as a nucleophile, the use of a base is optional. When an aminogroup is the nucleophile, then a base is not required.

The ring opening polymerization can be carried out with any suitablebase, for example, a base selected from potassium carbonate, sodiumcarbonate, cesium carbonate, sodium tertiary butoxide, potassiumtertiary butoxide, tetramethylammonium hydroxide, ammonium hydroxide,tetrabutylammonium hydroxide, sodium hydroxide, potassium hydroxide,lithium hydroxide, barium carbonate, barium hydroxide, cesium hydroxide,lithium carbonate, magnesium carbonate, magnesium hydroxide, sodiumamide, lithium amide, and combinations thereof.

In accordance with an embodiment, the ring opening polymerization can becarried in a suitable solvent, particularly a polar aprotic solvent.Examples of suitable solvents include N, N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone, andmixtures thereof.

The amount of the aromatic hydrophobic polymer, glycidol, and allylglycidyl ether can be present in the polymerization medium at anysuitable concentration, for example, each can be present at aconcentration of about 5% to about 60% or more, preferably about 10% toabout 50%, and more preferably about 20% to about 40%, by weight. In anembodiment, the concentration of each is about 30% by weight.

The ring opening polymerization is conducted such that the ratio of thehydrophobic polymeric segment to glycidol and allyl glycidyl ether inthe reaction mixture is preferably about 1:0.1:0.1 to about 1:2:2, morepreferably about 1:0.7:0.7 to about 1:1.2:1.2, and even more preferablyabout 1:0.8:0.8.

The ring opening polymerization is conducted at a suitable temperature,for example, from 25° C. to about 130° C., preferably about 50° C. toabout 120° C., and more preferably about 90° C. to 110° C.

The polymerization can be carried out for any suitable length of time,for example, about 1 hr to about 100 hrs, preferably about 2 hrs toabout 40 hrs, more preferably about 3 hrs to about 20 hrs. Thepolymerization time can vary depending on, among others, the degree ofpolymerization desired and the temperature of the reaction mixture.

The block copolymer can be isolated from the reaction mixture byprecipitation with a nonsolvent, e.g., methanol, ethanol, orisopropanol. The resulting polymer is dried to remove any residualsolvent or nonsolvent.

In the above block copolymer of the formula: A-B-A (I) or A-B (II), oneor more of the allyl groups of the copolymer can be replaced with1,2-dihydroxypropyl group or a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X is agroup selected from an acidic group, a basic group, a cation, an anion,a zwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy,aldehydo, amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of theformula —C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc),or a salt thereof, by reacting the block copolymer with an agentselected from an oxidizing agent, a carboxyl alkane thiol or a saltthereof, a sulfonic alkane thiol or a salt thereof, a(dialkylamino)alkane thiol or a salt thereof, a haloalkane thiol,hydroxyalkane thiol, an acyl alkane thiol, an alkoxy alkane thiol, analkylthio alkane thiol, an aldehydo alkane thiol, an amidoalkane thiol,a carbamoyl alkane thiol, an ureido alkane thiol, a cyanoalkane thiol, anitro alkane thiol, an epoxy alkane thiol, cysteine, an acyl cysteine,an aminoalkane thiol or a salt thereof, an alkylamino alkane thiol, adialkylaminoalkane thiol, and a sulfonic alkylammonium alkane thiol or asalt thereof.

The block copolymers can be characterized by any suitable analyticaltechnique. For example, the amount of hydrophobic polymeric segment andthe amount of the glycidol block (polyglycerol) can be determined byproton NMR spectroscopy.

The invention further provides a method for preparing a hydrophilicporous membrane comprising:

(i) providing a polymer solution comprising a solvent, said aromatichydrophobic polymer, and said block copolymer;

(ii) casting the polymer solution as a thin film;

(iii) subjecting the thin film to phase inversion to obtain a porousmembrane; and optionally

(iv) washing the porous membrane.

The polymer solution contains a polymer and a block copolymer as awetting agent. Typical polymer solutions comprise at least one solvent,and may further comprise at least one non-solvent. Suitable solventsinclude, for example, N,N-dimethylformamide (DMF); N,N-dimethylacetamide(DMAc); N-methyl pyrrolidone (NMP); dimethyl sulfoxide (DMSO), methylsulfoxide, tetramethylurea; dioxane; diethyl succinate; chloroform; andtetrachloroethane; and mixtures thereof. In accordance with anembodiment, the polymer solution contains N,N-dimethylformamide,N-methylpyrrolidone, or a mixture thereof, as the solvent.

Suitable nonsolvents include, for example, water; various polyethyleneglycols (PEGs; e.g., PEG-200, PEG-300, PEG-400, PEG-1000); variouspolypropylene glycols; various alcohols, e.g., methanol, ethanol,isopropyl alcohol (IPA), amyl alcohols, hexanols, heptanols, andoctanols; alkanes, such as hexane, propane, nitropropane, heptanes, andoctane; and ketone, ethers and esters such as acetone, butyl ether,ethyl acetate, and amyl acetate; acids, such as acetic acid, citricacid, and lactic acid; and various salts, such as calcium chloride,magnesium chloride, and lithium chloride; and mixtures thereof.

Typical casting solutions contain the polymer in the range of about 10wt % to about 35 wt % resin, in the range of from about 0.1 to about 10wt %, preferably about 0.2% to about 2%, and more preferably about 0.3%to about 1% of the hydrophilic block copolymer, in the range of fromabout 0 to about 90 wt % NMP, in the range of from about 0 to about 90wt % DMF, and in the range of from about 0 to about 90 wt % DMAc.

Suitable components of solutions are known in the art. Illustrativesolutions comprising polymers, and illustrative solvents and nonsolventsinclude those disclosed in, for example, U.S. Pat. Nos. 4,629,563;4,900,449; 4,964,990, 5,444,097; 5,846,422; 5,906,742; 5,928,774;6,045,899; and 7,208,200.

For example, membrane samples can be prepared through a solutionprocesses involving non-solvent-induced polymer precipitation, either bywater vapor diffusion or direct quenching in water. Typically, asolution of the polymer, e.g., PES or PPESK, is prepared first withsolvent DMAC or DMAC/NMP, pore former PEG400 and other additives. Thesolution is applied to a glass plate using a doctor blade with 10˜15-milspace gap, evenly to form a film of polymer dope. The film is theneither placed in a chamber with controlled temperature, air velocity andhumidity, or directly immersed into a water bath with a presettemperature, allowing some time for the dope to transform into a solidfilm. The resulting solid film sample is leached in 50˜70%ethanol/water, hot water at a temperature range from 50° C. to 80° C.and then dried in oven at a temperature range from 50˜70° C. to afford asheet of porous polymer membrane.

As an example, a typical formulation consists of PPESK polymer resin atabout 15˜25 wt %, solvent (NMP/DMAC) of about 200˜300 phr, wettingpolymer agents at a typical range of 5˜25 phr, up to 50 phr. Pore formerPEG400 is introduced at a concentration ranging from 50 phr to 100 phr.Other additives at a low percentage 0.5˜3.0% can be used as needed foreach individual formulation.

In accordance with an embodiment, the polymer solution contains anaromatic hydrophobic polymer and a copolymer in a mass ratio of fromabout 20% to about 80% to about 80% to about 20%.

The polymer or casting solution is cast as a flat sheet on a glass plateor on a moving substrate such as a moving belt. Alternatively, thecasting solution is cast as a hollow fiber.

Phase inversion can be effected by any known method. Phase inversion caninclude evaporation of the solvent and nonsolvent (dry process);exposure to a nonsolvent vapor, such as water vapor, which absorbs onthe exposed surface (vapor phase-induced precipitation process);quenching in a nonsolvent liquid, generally water (wet process); orthermally quenching a hot film so that the solubility of the polymer issuddenly greatly reduced (thermal process).

In an embodiment, phase inversion is effected by exposing the castsolution to a non-solvent vapor, for example, an atmosphere ofcontrolled humidity, following which the cast solution is immersed in anonsolvent bath such as water bath.

Alternatively, hydrophobic membrane can be coated with a hydrophilicblock polymer. Thus, for example, a solution of the block copolymer iscoated on a porous membrane formed from an aromatic hydrophobic polymer,or a porous membrane dipped in a solution of the block copolymer, andoptionally, heated, to obtain a hydrophilic modified porous membrane.

As illustrated in FIG. 3, the microstructure of the porous membrane inaccordance with an embodiment of the invention includes the hydrophilicpolymeric segment 3 on the pore surfaces of the membrane, therebyimproving the hydrophilicity of the membrane. The aromatic hydrophobicpolymeric segment 2 of the block copolymer orients itself with thearomatic hydrophobic polymer 1.

Porous membranes according to embodiments of the invention have acritical wetting surface tension (CWST0 of about 70 to about 90 dynes/cmor more, for example, 72, 74, 76, 78, 80, 82, 84, or 86 dynes/cm.

Porous membranes according to embodiments of the invention find use inas microfiltration or ultrafiltration membranes or in the preparation ofnanofiltration membranes, reverse osmosis membranes, gas separationmembranes, pervaporation or vapor permeation membranes, dialysismembranes, membrane distillation, chromatography membranes, and/orforward osmosis membranes and pressure retarded osmosis membranes.

Porous membranes according to embodiments of the invention have a poresize of about 0.05 μm to about 10 μm and find use as microfiltrationmembranes. Porous membranes according to certain embodiments of theinvention have a pore size of about 1 nm to about 0.5 μm and find use asnanofiltration membranes.

Porous membranes according to embodiments of the invention can be usedin a variety of applications, including, for example, diagnosticapplications (including, for example, sample preparation and/ordiagnostic lateral flow devices), ink jet applications, filtering fluidsfor the pharmaceutical industry, filtering fluids for medicalapplications (including for home and/or for patient use, e.g.,intravenous applications, also including, for example, filteringbiological fluids such as blood (e.g., to remove leukocytes)), filteringfluids for the electronics industry (e.g., filtering photoresist fluidsin the microelectronics industry), filtering fluids for the food andbeverage industry, clarification, filtering antibody- and/orprotein-containing fluids, filtering nucleic acid-containing fluids,cell detection (including in situ), cell harvesting, and/or filteringcell culture fluids. Alternatively, or additionally, membranes accordingto embodiments of the invention can be used to filter air and/or gasand/or can be used for venting applications (e.g., allowing air and/orgas, but not liquid, to pass therethrough). Membranes according toembodiments of the inventions can be used in a variety of devices,including surgical devices and products, such as, for example,ophthalmic surgical products.

In accordance with embodiments of the invention, the porous membrane canhave a variety of configurations, including planar, flat sheet, pleated,tubular, spiral, and hollow fiber.

Porous membranes according to embodiments of the invention are typicallydisposed in a housing comprising at least one inlet and at least oneoutlet and defining at least one fluid flow path between the inlet andthe outlet, wherein at least one inventive membrane or a filterincluding at least one inventive membrane is across the fluid flow path,to provide a filter device or filter module. In an embodiment, a filterdevice is provided comprising a housing comprising an inlet and a firstoutlet, and defining a first fluid flow path between the inlet and thefirst outlet; and at least one inventive membrane or a filter comprisingat least one inventive membrane, the inventive membrane or filtercomprising at least one inventive membrane being disposed in the housingacross the first fluid flow path.

Preferably, for crossflow applications, at least one inventive membraneor filter comprising at least one inventive membrane is disposed in ahousing comprising at least one inlet and at least two outlets anddefining at least a first fluid flow path between the inlet and thefirst outlet, and a second fluid flow path between the inlet and thesecond outlet, wherein the inventive membrane or filter comprising atleast one inventive membrane is across the first fluid flow path, toprovide a filter device or filter module. In an illustrative embodiment,the filter device comprises a crossflow filter module, the housingcomprising an inlet, a first outlet comprising a concentrate outlet, anda second outlet comprising a permeate outlet, and defining a first fluidflow path between the inlet and the first outlet, and a second fluidflow path between the inlet and the second outlet, wherein at least oneinventive membrane or filter comprising at least one inventive membraneis disposed across the first fluid flow path.

The filter device or module may be sterilizable. Any housing of suitableshape and providing an inlet and one or more outlets may be employed.

The housing can be fabricated from any suitable rigid imperviousmaterial, including any impervious thermoplastic material, which iscompatible with the fluid being processed. For example, the housing canbe fabricated from a metal, such as stainless steel, or from a polymer,e.g., transparent or translucent polymer, such as an acrylic,polypropylene, polystyrene, or a polycarbonate resin.

The following examples further illustrate the invention but, of course,should not be construed as in any way limiting its scope.

Example 1

This example illustrates the preparation of a block copolymer comprisingpolyethersulfone segment as block B and a copolymer of glycidol andallyl glycidyl ether as block A, for preparing hydrophilic porousmembranes in accordance with an embodiment of the invention.

BASF ULTRASON™ E6020 (500 g) polyethersulfone was added slowly to DMAc(1.5 L) in a 3 L reactor fitted with an overhead stirrer at 110° C.After complete dissolution of the polymer, K₂CO₃ (12.5 g) was added.After additional 2.5 hrs of stirring at 110° C. a mixture of allylglycidyl ether (400 mL) and glycidol (100 mL) were added, and thereaction mixture stirred at 110° C. for 12 hours. The hot reactionmixture was added slowly to vigorously stirred distilled water (15 L).The product obtained was filtered, and further stirred in ethanol (5 L)overnight. The precipitate was filtered, washed with ethanol (2 L) anddried in a vacuum oven at 50° C. overnight to yield 760 g of the blockcopolymer product (PES-Pg/PolyAGE) with 61 mol % of PES block and 39 mol% of block A containing polymerized glycidol and allyl glycidyl ether,as determined by proton NMR spectroscopy.

Example 2

This example illustrates the preparation of another block copolymercomprising polyethersulfone segment as block B and a copolymer ofglycidol and allyl glycidyl ether as block A, for preparing porousmembranes in accordance with an embodiment of the invention.

Sumitomo 5003PS (200 g) polyethersulfone was added slowly to DMAc (0.5L) at 110° C. After complete dissolution of the polymer, K₂CO₃ (12.5 g)was added. After additional 2.5 hrs of stirring at 110° C. a mixture ofallyl glycidyl ether (160 mL) and glycidol (40 mL) were added, and thereaction mixture stirred at 110° C. for 12 hours. The hot reactionmixture was added slowly to vigorously stirred distilled water (7 L).The product obtained was filtered, and further stirred in ethanol (1.5L) overnight. The precipitate was filtered, washed with ethanol (0.75 L)and dried in a vacuum oven at 50° C. overnight to yield 260 g of theblock copolymer product, PES-Pg/PolyAGE, with 57 mol % of PES and 43 mol% of block A containing polymerized glycidol and allyl glycidyl ether,as determined by proton NMR spectroscopy.

Example 3

This example illustrates the preparation of a block copolymer comprisingpolyethersulfone segment as block B and a copolymer of glycidol andallyl glycidyl ether where one or more allyl groups have been replacedwith a hydrophilic group, constituting block A, PES-Pm-MEA, forpreparing porous membranes in accordance with an embodiment of theinvention.

30 g of PES-Pg/PolyAGE from Example 1 was dissolved in DMAc (100 mL) at80° C. After complete dissolution of the polymer, the solution waspurged with nitrogen for 5 minutes. Aminoethanethiol hydrochloride (3 g)and 2,2′-azobis(2-methylpropionamidine)dihydrochloride (50 mg) wereadded and the reaction mixture was stirred at 80° C. for 21 hours. Thehot reaction mixture was precipitated by drop-wise addition to ethanol(750 mL). The resulting precipitate was reconstituted in ethanol (250mL) and further stirred for 2 hours. The resulting precipitate wasfiltered and dried in a vacuum oven at 50° C. overnight to yield 32 g ofthe desired product, PES-Pm-MEA, with 61 mol % of PES, 28 mol % ofaminoethanethiol group and 11 mol % of allyl group, as determined byproton NMR spectroscopy.

Example 4

This example illustrates the preparation of another block copolymercomprising polyethersulfone segment as block B and a copolymer ofglycidol and allyl glycidyl ether where one or more allyl groups havebeen replaced with a hydrophilic group, constituting block A,PES-Pm-MDMAE, for preparing porous membranes in accordance with anembodiment of the invention.

20 g of PES-Pg/PolyAGE from Example 1 was dissolved in DMAc (160 mL) at80° C. After complete dissolution of the polymer, the solution waspurged with nitrogen for 5 minutes. 2-(dimethylamino)ethane thiolhydrochloride (15 g) and2,2′-azobis(2-methylpropionamidine)dihydrochloride (80 mg) were addedand the reaction mixture was stirred at 80° C. overnight. The hotreaction mixture was precipitated by drop-wise addition to IPA (550 mL).The resulting precipitate was further stirred in IPA (100 mL) for 2hours. The precipitate was filtered and washed with deionized water(1000 mL) followed by IPA (500 mL). The resulting product was dried in avacuum oven at 50° C. overnight yielding 23 g of the desired product,PES-Pm-MDMAE, with 61 mol % of PES, 34 mol % of dimethylamino-ethanethiol group and 5 mol % of remaining allyl group, as determined byproton NMR spectroscopy.

Example 5

This example illustrates the preparation of another block copolymercomprising polyethersulfone segment as block B and a copolymer ofglycidol and allyl glycidyl ether where one or more allyl groups havebeen replaced by a hydrophilic group, constituting block A, PES-Pm-MES,for preparing porous membranes in accordance with an embodiment of theinvention.

30 g of PES-Pg/PolyAGE from Example 1 was dissolved in DMAc (150 mL) at80° C. After complete dissolution of the polymer, the solution waspurged for five minutes. Sodium-2-mercaptoethansulfonate (25 g) and2,2′-azobis(2-methylpropionamidine)dihydrochloride (500 mg) were addedand the reaction mixture was stirred at 80° C. overnight. The hotreaction mixture was precipitated by drop-wise addition to IPA (250 mL).The precipitate was further stirred in IPA for 2 hours, filtered, anddried in a vacuum oven at 50° C. overnight. 34 g of the desired product,PES-Pm-MES, was obtained with 61 mol % of PES, 35 mol % ofmercaptoethanesulfonic acid and 4 mol % of allyl group, as determined byproton NMR spectroscopy.

Example 6

This example illustrates the preparation of another block copolymercomprising polyethersulfone segment as block B and a copolymer ofglycidol and allyl glycidyl ether where one or more allyl groups havebeen replaced by a hydrophilic group, constituting block A, PES-Pm-MPS,for preparing porous membranes in accordance with an embodiment of theinvention.

40 g of PES-Pg/PolyAGE from Example 1 was dissolved in DMAc (250 mL) at80° C. After complete dissolution of the polymer, the solution waspurged for five minutes. Mercaptopropane sulfonic acid sodium salt (25g) and 2,2′-azobis(2-methylpropionamidine)dihydrochloride (500 mg) wereadded and the reaction mixture was stirred at 80° C. overnight. The hotreaction mixture was precipitated by drop-wise addition to IPA (750 mL).The precipitate was further stirred in IPA for 2 hours, filtered, anddried in a vacuum oven at 50° C. overnight. 48 g of the desired product,PES-Pm-MPS, was obtained with 61 mol % of PES, 36 mol % ofmercaptopropanesulfonic acid and 3 mol % of allyl group, as determinedby proton NMR spectroscopy.

Example 7

This example illustrates the preparation of another block copolymercomprising polyethersulfone segment as block B and a copolymer ofglycidol and allyl glycidyl ether where one or more allyl groups havebeen replaced by a hydrophilic group, constituting block A, PES-Pm-MAA,for preparing porous membranes in accordance with an embodiment of theinvention.

20 g of PES-Pg/PolyAGE from Example 1 was dissolved in DMAc (100 mL) at80° C. After complete dissolution of the polymer, the solution waspurged for five minutes. Mercaptoacetic acid sodium (15 g) and2,2′-azobis(2-methylpropionamidine)dihydrochloride (200 mg) were addedand the reaction mixture was stirred at 80° C. overnight. The hotreaction mixture was precipitated by drop-wise addition to ethanol (550mL). The precipitate was further stirred in ethanol for 2 hours,filtered, and dried in a vacuum oven at 50° C. overnight. 22 g ofproduct, PES-Pm-MAA, was obtained with 61 mol % of PES, and 39 mol % ofmercaptoacetic acid, as determined by proton NMR spectroscopy. No freeallyl group was observed.

Example 8

This example illustrates the preparation of porous membranes comprisinga blend of PES and the polymer of Example 1 (PES-Pg/PolyAGE) or a blendof PES and the copolymer of Example 5 (PES-Pm-MES).

Membrane casting solutions were prepared by mixing the polymers,solvent, nonsolvent, and pore former, as set forth in Table 1 below.

TABLE 1 Compositions of Membrane Casting Solutions PES-Pg/PolyAGEPES-Pm-MES from from Example 1 Example 5 % % PEG 400 64.50 64.50 H₂O3.00 3.00 DMF 10.00 10.00 NMP 7.60 7.60 PES 6.95 8.55 Glycerin 1.00 1.00PES-P 6.95 5.25 Total 100.00 100.00

The casting solutions were cast as thin films at 10-mil dope thicknessusing vapor-induced phase separation process, with a casting temperatureof 30° C., relative humidity of 70%, and dry bulb temperature of 25° C.The dopes were placed in a water vapor chamber for 15 seconds andimmersed in water bath at a temperature of 13° C.

CWST was measured on the dried membranes. Samples of the membrane werealso tested for IPA extractables. 6 discs of 47 mm diameter were driedfor 1 hour at 80° C. and then Soxhlet extracted with IPA for 3 hoursfollowed by a final 1 hour dry cycle at 80° C. The % extractables werecalculated. The CWSTs were again measured on several of the discs afterthe IPA extraction. A polyethersulfone prepared using polyvinylpyrrolidone as a wetting agent was used as a control. The resultsobtained are set forth in Table 2.

TABLE 2 Properties of Membranes PES-PVP **50% PES-Pg/ **25% PES- K90PolyAGE from Pm-MES from Control Example 1 Example 5 CWST 87 90 87(dynes/cm) IPA Extractables 2.44 1.14 1.33 (%) **Relative to the amountof PES matrix.

As indicated, the porous membrane prepared with PES-Pg/PolyAGE fromExample 1 had a CWST of 90 dynes/cm and a low extractables level of1.14%; it was instantly wetted by water. The porous membrane preparedwith PES-Pm-MES from Example 5 had a CWST of 90 dynes/cm and a lowextractables level of 1.33%; it was also instantly wetted by water. Forcomparison, a polyethersulfone membrane prepared usingpolyvinylpyrrolidone has a CWST of 87 dynes/cm; however, the IPAextractables were high at 2.44%.

The morphology of the membranes was characterized using a Hitachi-3400IISEM with samples pre-sputtered with platinum/gold. SEM images of thecross-section of the porous membrane prepared from a blend of PES andPES-Pg/PolyAGE are shown in FIGS. 1A and 1B. SEM images of thecross-section of the porous membrane prepared from a blend of PES andPES-Pm-MES are shown in FIGS. 2A and 2B. The membranes contained highlyinterconnected pore structure with pores extending from one side to theother.

Example 9

This example illustrates the preparation of porous membranes comprisinga blend of PPESK and PES-Pg/PolyAGE as wetting agent.

A casting solution containing a PPESK resin at 20 wt %, solvent NMP:DMAc(v/v) at 300 phr, the PES-Pg/PolyAGE of Example 1 at 15 phr was preparedand cast as a 15 mil thick film at 28° C., air temperature 32° C.,relative humidity 72%. The dope was placed in an environmental chamberfor 15 seconds and immersed in water at room temperature. The morphologyof the membrane was characterized by SEM. FIG. 4A depicts the SEM imageof the cross-section of a membrane in accordance with an embodiment ofthe invention. FIG. 4B depicts a higher magnification SEM image of theimage depicted in FIG. 4A. The membrane had a CWST of 76 dynes/cm. Themembrane had an unsymmetrical pore structure distribution from side toside. The pores were in cellular forms with low interconnectivity.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and “at least one” andsimilar referents in the context of describing the invention (especiallyin the context of the following claims) are to be construed to coverboth the singular and the plural, unless otherwise indicated herein orclearly contradicted by context. The use of the term “at least one”followed by a list of one or more items (for example, “at least one of Aand B”) is to be construed to mean one item selected from the listeditems (A or B) or any combination of two or more of the listed items (Aand B), unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

1. A porous membrane comprising a block copolymer of the formula: A-B-A(I) or A-B (II), wherein block A is: (i) a copolymer of glycidol andallyl glycidyl ether, the copolymer having one or more allyl groups; or(ii) a copolymer of glycidol and allyl glycidyl ether, wherein one ormore of the allyl groups of the copolymer have been replaced with1,2-dihydroxypropyl group or a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X isselected from an acidic group, a basic group, a cation, an anion, azwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy, aldehydo,amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of the formula—C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc), or asalt thereof; and block B is an aromatic hydrophobic polymeric segment.2. The porous membrane of claim 1, wherein block A is (i) a copolymer ofglycidol and allyl glycidyl ether, the copolymer having one or moreallyl groups.
 3. The porous membrane of claim 1, wherein block A is (ii)a copolymer of glycidol and allyl glycidyl ether, wherein one or more ofthe allyl groups of the copolymer have been replaced with1,2-dihydroxypropyl group or a group of the formula:—(CH₂)_(a)—S—(CH₂)_(b)—X, wherein a is 3 and b is 1 to 3, and X isselected from an acidic group, a basic group, a cation, an anion, azwitterion, halo, hydroxyl, acyl, acyloxy, alkylthio, alkoxy, aldehydo,amido, carbamoyl, ureido, cyano, nitro, epoxy, a group of the formula—C(H)(COOH)(NH₂), and a group of the formula —C(H)(COOH)(NHAc), or asalt thereof.
 4. The block copolymer of claim 1, wherein, as X, theacidic group is sulfonic acid or carboxylic acid, the basic group is anamino group, an alkylamino group, or a dialkylamino group, the cation isa quaternary ammonium group, and the zwitterion is a quaternary ammoniumalkyl sulfonate group of the formula —N⁺(R¹R²)(CH₂)_(c)SO₃ ⁻, wherein R¹and R² are alkyl groups and c is 1 to
 3. 5. The porous membrane of claim1, wherein the aromatic hydrophobic polymeric segment is selected frompolysulfone, polyethersulfone, polyphenylene ether, polyphenylene oxide,polycarbonate, poly(phthalazinone ether sulfone ketone), polyetherketone, polyether ether ketone, polyether ketone ketone, polyimide,polyetherimide, and polyamide-imide.
 6. The porous membrane of claim 5,wherein the aromatic hydrophobic polymeric segment comprisespolyethersulfone.
 7. The porous membrane of claim 1, wherein block A isa branched copolymer.
 8. The porous membrane of claim 1, which has thefollowing structure:

wherein n is about 10 to about
 1000. 9. The porous membrane of claim 1,which has the following structure:

wherein R is allyl or —(CH₂)_(b)—X wherein b is 1 to 3 and n is about 10to about
 1000. 10. The porous membrane of claim 9, wherein R is—(CH₂)_(b)—X.
 11. The porous membrane of claim 9, wherein X is selectedfrom amino, dimethylamino, —CH₂CH₂SO₃H, —CH₂CH₂CH₂SO₃H, —CH₂CO₂H, and—CH₂CH₂N⁺(CH₃)₃, and combinations thereof.
 12. The porous membrane ofclaim 1, wherein block A is present in an amount of about 20% to about50 mol % and block B is present in an amount of about 50% to about 80mol %.
 13. The porous membrane of claim 1, which has one of thefollowing structures:

wherein n is about 10 to about
 1000. 14. A method of preparing a porousmembrane according to claim 1, comprising: (i) providing a polymersolution comprising a solvent, said aromatic hydrophobic polymer, andsaid block copolymer; (ii) casting the polymer solution as a thin film;(iii) subjecting the thin film to phase inversion to obtain a porousmembrane; and optionally (iv) washing the porous membrane.
 15. Themethod of claim 14, wherein the polymer solution containsN,N-dimethylformamide, N-methylpyrrolidone, or a mixture thereof, as thesolvent.
 16. The method of claim 14, wherein the polymer solutionfurther contains a nonsolvent and/or a pore former.
 17. The method ofclaim 16, wherein the nonsolvent is water.
 18. The method of claim 16,wherein the pore former is polyethylene glycol, glycerin, or a mixturethereof.
 19. The method of claim 14, wherein said aromatic hydrophobicpolymer and the copolymer are present in a mass ratio of from about 20%to about 80% to about 80% to about 20%.